The long term objective of this research program is to gain a better understanding of the molecular basis for the programmed sequences that are involved in differentiation and morphogenesis. To this end we make use of a now well established and unique model system for which we have described extensive and simultaneous changes in gene expression and cell hair construction. I have isolated in a pure form the protein which is almost certainly the major component of epicuticle (the most external and impervious part of the exoskeleton). Purification of several other proteins involved in later stages of hair construction is in progress. All of these proteins are to be used for the preparation of specific antibodies and for the determination of sufficient sequences for the preparation of DNA probes for the genes involved. Besides protein isolations work continues to determine further details of hair morphogenesis by high resolution electron microscopy. We expect eventually to be able to convert the correlations obtained between protein synthesis patterns and structure deposition into facts by use of antibodies obtained. Some of the structure formation evidently involves secondary processing of proteins and we have shown that this may be autoproteolytic in some cases. We plan to continue exploration of this interesting property of several of the proteins we are dealing with.